Form 21-4138 to explain finances

Do I need to fill out form 21-4138 to explain the separate bank account with $10, 000 that came from a life insurance policy that matured at age 85 ( He is 90 now) and he cashed in but wants to still set aside for funeral expenses. I will include bank statement. Do I need to fill out that form or could this information be included in the cover letter?